Despite the ubiquity of neutral lipid droplets and their importance in obesity and other diseases, we know very little about their structure, synthesis, and turnover. A prime candidate for regulating these processes is adipocyte differentiation-related protein (ADRP). ADRP is up-regulated in parallel with stored lipids during droplet formation and is present on the surface of lipid droplets from the earliest time of their synthesis. Furthermore, exogenous expression of ADRP leads to an increase in neutral lipid mass and the over-accumulation of lipid droplets. While these studies strongly suggest a role for ADRP in promoting lipid accumulation, the precise mechanism by which ADRP affects lipid storage is unknown. Therefore, in the proposed studies, we will determine whether ADRP expression prevents hydrolysis of stored lipid or increases the rate of lipid synthesis. We will determine if ADRP is required for lipid droplet biosynthesis. If droplets form in the absence of ADRP, we will explore differences in their protein or lipid composition. Finally, our experiments will identify signals that target ADRP to the lipid droplet surface. These results will contribute to our understanding of the mechanisms controlling lipid droplet accumulation.